Zinc alloy



Patented Jan. 20, 1931 UNITED STATES PATENT OXFFVICE ZINC ALLOY Io Drawing.

Our invention relates to new and useful alloys of zinc whose advantages will be hereinafter set forth. The alloys are prepared by adding to 100 parts of zinc from A to 2 parts of copper and a small proportion of ilver. The alloys should be free from aluminum and magnesium, preferably completely, but in any event in proportions so substantial as to affect adversely their valuable characteristics.

The use of zinc, particularly when rolled into the form of sheets or strips, is limited because of its low tensile strength, its slight hardness, and the rapid dulling of its surface. These disadvantages are overcome if there be added to zinc both copper, in the proportion of A to 2% of the amountof zinc, and silver in the proportion of .1% to 20% of the copper; An alloy thus produced may be rolled into sheets and strips whose surface can be brought to an attractive condition by polishing, the polished surface maintaining its lustre, and which have a -much higher tensile strength than sheets or strips rolled from zinc or known zinc base alloys. At the same time the natural advantages of the zinc are not reduced, in any event,

to develop cracks and to should, however,

to any appreciable or substantial extent.

When used as a base metal for fixing etch ings, the etching process can be carried out more rapidly than with ordinary zinc. The use of the silver toughens the alloy, and nder some circumstances increases its ductili y.

The zinc used in the production of the alloy may be a high grade zinc but for practical purposes we prefer to use the lower grades of commercial slab zinc or spelter which not contain ingredients which detrimentally affect the alloy. For instance the presence cadmium or 04% of iron renders the zinc too brittle for rolling into thin gauges and the presence of over ,6% of lead so decreases the tensile strength of the alloy that thin sheets rolled therefrom will tear even inthe rolling process. The presence of even a small trace of aluminum causes the alloy, after'rolling, disintegrate. For practical purposes we prefer to use a grade of spelter known in the trade as intermediincorporated with the zinc,

silver (or 1.7% relative to copper) of more than .6% of Application med October 18, 1929. Serial No. 400,724.

ate, whose maximum iron content is 03%, maximum lead ,content 2%, and maximum cadmium content .5%, but not more than a total of .5% of all such metals, and which is substantially free from aluminum and magnesium.

We may, however, use to advantage the grade of spelter known as brass special or the grade known as high grade.

The exact proportion of copper and of silver will depend upon the particular qualit1es of the alloy to be produced and also upon the various conditions of the process, for instance, rolling, to which the alloy is to be subjected. The particular proportions may easily be adjusted by simple experiment until the correct proportion suitable for the desired alloy is determined.

Example About 6 tons (12,000 pounds) of slab s elter--brass special-containing in addition' to zinc iron- 02% lead, .6%, and cadmium 08%, are charged into a coal fired tank furnace and the temperature of the furnace maintained at a temperature of 825 F. When the slabs are completely melted, form- AND FLOYD A. WARREN, or man, rumors, ,AS-

or cnrcaemaumors, A conrona'rron or ing a bath of molten zinc, i. s. after about six hours, the dross is carefully skimmed ofi and 30 pounds (or 25%) of copper in the form of wire are added and stirred into the molten metal. After the copper has been thoroughly 8 ounces of are added in the form of pellets and stirred into the bath of molten metal. When both the copper and the silver are incorporated with the zinc, the molten alloy is cast into plates suitable for rolling. These plates after annealing in the manner usual -w1th ordinary zinc i. e. by heating to 350400 G. are passed-through roughing and finishing rolls, in the same manner as with ordinary zinc, to form sheets or strips.

It would be possible if desired toincorporate the silver first with the copper and to add the alloy thus produced, either in liquid or solid form, to the molten zinc.

The new .alloy thus'produced compares app o imately as follows with ordinary rolled 1,789 854 P ovided 1n the same mlfig f and zinc e e rolled New,

Hardness, Rockwell. 97 F! Tensile strength per sq. inch. 80,300 lbs. 26,!!!) Ill. pers inch 42,300 lbs. 82,!!!) lbs. Dynanac ductility 850 860 Bends g 10 It will be noted that the hardness of our alloy is about 10 points greater by the Rockwell scale than ordina rolled zinc and that the tensile. strength o our alloy both with and across the grain is appreciably greater than that of ordinary zinc. At the same time the ductility of the alloy, as indicated by the readings on the dynamic testing machine and on the bending machine, shows that the increase in hardness and tensile strength has not been obtainedat a sacrifice of ductllity.

The alloy has a higher resistance in the electro-magnetic fields than ordinary zinc without having its ductility impaired, in any event, to any substantial degree.

Attention is called to the fact that these physical tests are significant only when compared with ordinary zinc rolled under identi- 30 cal conditions. The alloy of the example would, if rolled to a thinner gauge, have its tensile strength increased to 36,400 pounds, its dynamic ductility to 370, and its Rochwell hardness to 97%.

m We claim:

1. As a composition of matter an alloy characterized by the fact that it is of substantially greater hardness than zinc composed of zinc 100 parts, copper to 2 parts and an a preciable quantity of silver, such quantity being less than the amount of copper used.

2. As a composition of matter an alloy composed of zinc 100 parts, cofper ,4 to 2 parts and silver .1% to o the copper. 45 3. Asa new article of manufacture a mechanically worked zinc roduct made of a zinc base alloy composed of zinc 100 parts, copper A to 2 parts, and an appreciable quantity of silver, such' quantity being less than the copper.

LELAND E. WEMPLE. FLOYD A. WARREN. 

